7.23 - Perfect Competition
Market structures and their efficiency
Market structures describe the different ways in which markets are organised, based on factors such as the number of firms, barriers to entry, and product differentiation. These structures are evaluated on their efficiency, which refers to how well resources are used to maximise output and consumer welfare.
The four main market structures
Markets are classified into four types, ranging from the most competitive to the least competitive:
- Perfect competition - The most competitive structure, serving as a benchmark for efficiency.
- Monopolistic competition - Features many firms with some product differentiation.
- Oligopoly - Dominated by a few large firms with significant market power.
- Monopoly - The least competitive, with a single firm controlling the market.
How efficiency is assessed in market structures
Efficiency in market structures is measured by analysing prices, revenue, output levels, and profits in both the short run (where some factors are fixed) and the long run (where all factors can change).
Characteristics of perfect competition
Perfect competition is a theoretical model that represents the most competitive end of the market structure spectrum.
Key features of perfect competition
- Many buyers and sellers - The market includes a large number of participants with perfect knowledge.
- Price takers - Firms have no control over the market price and must accept it as given.
- Homogeneous products - Goods or services are identical in quality, features, and consumer perception.
- Freedom of entry and exit - There are no barriers preventing new firms from entering or existing firms from leaving the market.
- Perfect information - All participants have complete knowledge of prices, product details, and production methods.
Real-world examples approximating perfect competition
While no market is perfectly competitive, some come close:
- Cryptocurrency trading platforms - Thousands of traders buy and sell identical units of digital currencies, with prices determined by overall market forces.
- Online markets for standardised components - Sellers offer identical electronic parts based on uniform specifications, allowing buyers to choose based solely on price.
Price and revenue relationships in perfect competition
In perfect competition, the demand curve facing an individual firm is perfectly elastic, meaning the firm can sell any quantity at the prevailing market price without affecting it.
Demand and revenue curves
Firms face a horizontal demand curve at the market price. Average revenue (AR) equals the price per unit, as it is the revenue per unit sold. Marginal revenue (MR) equals AR and the price, since each additional unit sold brings in the same revenue as the previous one.
This relationship is expressed as:
Where:
- D = Demand
- AR = Average revenue
- MR = Marginal revenue
- P = Price
Output decisions and profit in perfect competition
Firms in perfect competition decide their output levels to maximise profits, considering costs and revenues in both the short run and long run.
Profit maximisation rule
Firms produce where marginal cost (MC) equals marginal revenue (MR), which also equals the price:
Where:
- MC = Marginal cost (additional cost of producing one more unit)
- MR = Marginal revenue (additional revenue from selling one more unit)
Types of profit in perfect competition
- Supernormal profit - Occurs when total revenue exceeds total cost, possible in the short run.
- Normal profit - Achieved when total revenue equals total cost, covering opportunity costs.
- Losses - Happen when total cost exceeds total revenue.
Short-run losses and shutdown decisions
In the short run, firms may incur losses but continue operating if the price covers average variable cost (AVC).
Key concepts:
- Shutdown point - Occurs at the minimum point of the AVC curve; below this, losses exceed fixed costs, and firms shut down temporarily.
- The short-run supply curve is the part of the MC curve above the minimum AVC.
Long-run equilibrium
Supernormal profits attract new firms due to no entry barriers, increasing market supply and lowering prices until only normal profits remain.
Factors affecting profit differences
Firms with lower average total costs (ATC) earn higher profits. The main way to increase profits is by improving productivity to reduce ATC, as all firms face the same market price.
Efficiency outcomes in perfect competition
Perfect competition achieves high efficiency, making it a benchmark for other structures.
Types of efficiency achieved
- Productive efficiency - Firms produce at the lowest point of their ATC curve in the long run, minimising costs per unit.
- Allocative efficiency - Output occurs where price equals MC, ensuring resources are allocated to meet consumer demand optimally.
Why perfect competition promotes efficiency
Perfect competition promotes efficiency because supernormal profits are temporary, competed away by new entrants. Firms lack market power, preventing exploitation of consumers through high prices. This efficiency is used to assess less competitive structures, where market power can lead to higher prices and reduced output.